Radial tire having interposed plies at tread reinforcement edges

ABSTRACT

A radial tire has a tread reinforcement of two plies with staggered edges. Fittings of wedge-shaped cross section are interposed between the carcass and the tread reinforcement at each edge of the tread reinforcement. Each fitting comprises two interposed plies of different widths. The interposed plies comprise cords forming a triangulated structure with the radial carcass cords and extending laterally beyond the tread reinforcement.

United States Patent 1 Boileau 1 Feb. 20 1973 [54] RADIAL TIRE HAVINGINTERPOSED [56] References Cited E D E NF R E E T PLIES AT TR A R I O CM N UNITED STATES PATENTS EDGES 3,554,261 l/l97l Mirtain et al ..l52/36l[75] Invent Clemmm Ferrand 2,331,323 10/1943 Jahant ..152/357 [73]Assignee: Compagnie Generale des Etablisse- Primary Examiner-Gerald M.Forlenza ments Michlen, raison sociate Assistant ExaminerGeorge H.Libman Mi h lin & Ci (11 mg Attorney-Brumbaugh, Graves, Donohue &Raymond (Puy-de-Do mjfFEnce [22] Filed: March 1, 1971 [57] ABSTRACT Aradial tire has a tread reinforcement of two plies [21] Appl' ll9689with staggered edges. Fittings of wedge-shaped cross section areinterposed between the carcass and the [30] Forei n Application P i it Dt tread reinforcement at each edge of the tread reinforcement. Eachfitting comprises two interposed plies March 2, 1970 France ..7007456 ofdifferent widths. The interposed plies comprise cords forming atriangulated structure with the'radial [52] U.S. Cl ..152/36l carcasscords and extending laterally beyond the tread [51] Int. Cl ..B60c 9/64reinforcement [58] Field of Search ..l52/36l, 357, 356

7 Claims, 4 Drawing Figures PATENTED 3,717. 190

SHEET 10f 2 INVENTOR. JACQUES BOILEAU his ATTORNEYS PATENTEDFEBZOISBSHEET 2 BF 2 LONGITUDINAL DIRECTION ISA RADIAL TIRE HAVING INTERPOSEDPLIES AT TREAD REINFORCEMENT EDGES BACKGROUND OF THE INVENTION Thisinvention relates to tires and, more particularly, to novel and highlyeffective tires of the radial type.

Radial tires comprise a reinforcement consisting of two parts: a carcasscomposed of radially arranged cords or cables and a tread reinforcementextending below the tread and comprising several plies of intersectingcords or cables arranged in directions differing only slightly, if atall, from the longitudinal direction.

In this type of tire, the regions of the edges of the treadreinforcement are highly stressed, particularly when traveling at highspeed. When a tire under load is caused to roll at an increasingly highspeed until it becomes unusable, it is generally as a result of tearingor destruction of the bonding rubber between the carcass and one of theedges of the tread reinforcement that the unusable condition occurs. Itis obviously desirable to improve the speed limit, that is to sav, themaximum speed which the tire can withstand, since one at the same timeimproves its ability to withstand higher and higher forces.

Various arrangements which favor the bonding between the carcass and theedges of the tread and increase the limit speed of a radial tire areknown in the literature or in practice.

A first conventional arrangement consists in staggering the edges ofcrown plies; the crown plies are wider and/or extend farther from themiddle plane the closer they are to the carcass. This staggering of thecrown ply edges in the vicinity of the carcass produces a gradation ofthe rigidity of the tread reinforcement and favors a better bond withthe carcass.

Another arrangement which is currently employed, particularly in tireswith metal tread reinforcement, consists in imparting to the carcass andtread reinforcement different transverse curvatures: the carcass and thetread reinforcement are adjacent in the portion of the top close to themiddle plane; they diverge progressively towards the edges, the treadreinforcement having a shape which approaches the shape of a cylinder.Between the carcass and the tread reinforcement, in the regions of theedges of the latter, there are interposed fittings of wedge-shapedcross-section made of a rubber-base mixture having good properties ofresistance to tearing.

A final conventional arrangement, which is at times used, consists ofreinforcing the carcass by means of a narrow ply at each of the twoedges of the tread reinforcement. This narrow ply is made of cords orcables arranged at an angle intermediate the angle of the cords of thetop plies and that of the cords of the carcass. This arrangement isdescribed in detail in French Pat. No. 1,435,804 and in its US. Pat.counterpart, No. 3,386,487.

These various known arrangements produce a transition between sidewallswhich are relatively deformable since reinforced only by radial cordsand a crown which is relatively rigid since it is reinforced. by cordsarranged in at least three directions. They contribute to improving thebond between the carcass and the crown reinforcement and therefore thestrength of the tire when subjected to forces close to the limit whichit can withstand. They do not, however, provide a final solution, and itis still desirable further to improve the coherence between the variouselements of the reinforcement.

SUMMARY OF THE INVENTION An object of the present invention is toimprove the coherence between the various elements of the tirereinforcement. More particularly, an object of the invention is toprovide an increase in the limit velocity and correlative properties ofradial-carcass tires by improving the coherence between the carcass andthe tread reinforment, particularly in the case of a very rigid treadreinforcement consisting, for instance, of metal cables.

The foregoing and other objects are attained in accordance with theinvention by a tire which is provided with a radial carcass and a treadreinforcement comprising at least two plies and staggered edges, whichis adjacent the carcass in the central portion of the crown and spacedfrom the carcass and connected to it in the side portions of the crownby interposed fittings of wedge-shaped cross section. The tire ischaracterized in that each of the interposed fittings is formed by thesuperimposing of two plies of different widths the cords or cables ofwhich form a triangulated structure with the cords or cables of thecarcass and protrude laterally from the tread reinforcement so as tocomplete the staggering of the crown plies.

As can be seen, the invention provides an increase in the compactnessofthe reinforcement of the tire; the tread reinforcement and the carcass,in the side portions of the crown where they are not directly in contactwith each other, are connected to one another by a superimposing ofplies arranged in such a manner as to take up the difference intransverse curvature between the tread reinforcement and the carcass andform a triangulation with the cables of the carcass.

Experience shows that the arrangement thus described results in aneffective hooping of the carcass, assures improved connection to thetread reinforcement and improves the limit velocity and the strength ofthe tire without resulting in any loss from the point of view ofcomfort, endurance or wear.

The regions of the carcass to be reinforced in accordance with theinvention by means of interposed fittings formed of a plurality ofsuperimposed plies are limited to the side regions of the crown.

Preferably, in the central region of the crown, the tread reinforcementand the carcass are adjacent over a width corresponding approximately tohalf the width of the tire. One can, however, use as common element forthe two interposed fittings a single ply which extends over the entirewidth of the crown, in particular for reasons of convenience inmanufacture. This common element serves as the first or second ply inboth the lefthand and the right-hand interposed fitting, the other plyof each fitting being formed either by a separate ply or by the turningover of the edge of the common element.

It is advisable not to extend the interposed fittings too far into thesidewalls. While it is permissible to extend one of the pliesconstituting the interposed fitting into the sidewall, for instance overone-third or onehalf of the height of the sidewall even though at theprice of loss of comfort, it is necessary to avoid forming atriangulation with the carcass cables outside the region of the crown; atriangulation of the upper part of the sidewalls would make the tireuncomfortable and would decrease its endurance. In practice, theinterposed fittings protrude laterally beyond the tread reinforcementover a distance of the same order of magnitude as the stagger spacing ofthe crown ply edges, namely to 15 mm in the case of tires for passengercars, and in any event at most 15 percent of the width of the tread.

The preferred embodiments are further characterized by the followingfeatures:

a. The plies forming the interposed fittings consist of cords arrangedat an angle with the longitudinal direction of between and 30. Theimprovement obtained does not depend substantially on the value of thisangle within these limits. Slightly better results are obtained with anangle of 10. The order of superimposing of the plies forming theinterposed fitting is immaterial; it is unimportant whether the angle ofthe cords of the crown ply and those of the adjacent interposed ply arelarger or smaller; however, the resistance of the interposed fittings isincreased by adopting for the cords of the interposed fitting ply whichis closer to the carcass an angle larger than that made by the cords ofthe interposed fitting ply which is farther from the carcass.

b. The cords of the interposed fitting plies are of a material whichcontracts under heat, preferably polyamide. The choice of a materialwhich contracts under heat is justified by the fact that under theaction of the heating produced by the rolling of the tire, the cordscontract and their contraction results in a more active binding of thecarcass. Polyamides are preferred due to their good adherence to rubber,their great elasticity, their lightness and their strength.

c. The cords used have, in the case of passenger car tires, a diameterless than or equal to 0.5 mm and are arranged side by side at a distanceapart of less than '1 mm. The selection of such dimensions makes itpossible to miniaturize the group of plies forming the interposedfitting and accordingly to house the fitting between the carcass and thetread reinforcement without having to move the latter away from thecarcass in an undesirable fashion. The assembly of reinforcements(carcass, interposed fittings and tread reinforcement) thus form acompact assembly without undesirable spacing.

d. Two superimposed plies forming a wedge-shaped interposed fitting areobtained from a single ply folded in the shape of a U with unequal arms.The widths of the two arms are selected so as to permit the interposedfitting to assume a wedge-shaped cross section. The fold line isintended to be located on the side opposite the middle plane of thetire. Instead of a folded ply, it may be desirable, in order to simplifymanufacture, to use two separate plies; they are then preferablyarranged in such a manner that their ends are a few millimeters fromeach other on the side opposite the middle plane.

BRIEF DESCRIPTION OF THE DRAWING An understanding of additional aspectsof the invention can be gained from a consideration of the followingdetailed description of preferred embodiments thereof, in conjunctionwith the appended figures of the drawing, wherein:

FIG. 1 is a view in radial section of a first embodiment of a tire inaccordance with the invention;

FIG. 2 is a fragmentary view in radial section of another embodiment ofa tire in accordance with the invention;

FIG. 3 is a view in radial section of another embodiment of a tire inaccordance with the invention; and

FIG. 4 is a fragmentary developed plan view showing the relativeorientations of certain cords of plies laid in accordance with theinvention. 3

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows in radial sectiona tire I of size 165 X 380 ZX.

The tire has a crown 2, a tread 3 and two sidewalls 4. Its reinforcementcomprises a carcass 10 made of radially arranged rayon cords the ends ofwhich are wound around steel bead wires 5. Stiffeners 6 stiffen theregion of the sidewalls 4 adjacent the bead wires 5. The reinforcementof the tire further comprises a tread reinforcement including two pliesl2 and 13 of identical metal cables, each formed of four steel wires ofa diameter of 0.23 mm each. The ply 12 has a width of 130 mm and the ply13 a width of mm so that their edges are staggered. The cables arearranged in such a manner as to form an angle of 22 with the medianplane M-M' of the tire, from left to right in the case of the ply l2,and from right to left in the case of the ply 13.

Between the carcass 10 and the tread reinforcement there are arranged inaccordance with the invention two insertions 15, each composed of a plyof cables folded to form two sections 15A and 158. The section 15A has awidth of 27 mm and the section 153 a width of 18 mm. Each insertion as awhole protrudes laterally from the ply 12 by a width of about 8 mm. Thecables of these insertions are polyamide cables of 420 X 2 denier; theyhave a diameter of 0.4 mm, have a center-tocenter spacing of 0.6 mm andare arranged along an angle of 1 15 with the median plane M-M'. Thecords of the carcass 10 and of the sections 15A and 15B therefore form atriangulated structure, as illustrated in FIG. 4.

In the embodiment shown in FIG. 2, each insertion 15 is composed of twoseparate plies l6 and 17 composed of yarns inclined 15 in oppositedirections. The ply 16 has a width of 36 mm and the ply 17 a width of 25mm. The end of the ply l6 farther from the median plane M-M' protrudesbeyond the ply 17 by a width of about 3 mm. In its turn, the end of theply 17 which is farther from the median plane MM' protrudes beyond theply 12 by a distance of about 5 mm. Finally, the end of the ply 12protrudes beyond the ply 13 by a distance of about 5 mm. Otherwise, thetire of FIG. 2 is identical to that of FIG. 1; in particular, the cordsof the inserts 15 are identical and arranged in, the same manner as inFIG. 1.

Comparative maximum velocity tests have given the 2. Tire according toFIG. 1 222 km/hr 222 km/hr 227 km/hr 220 km/hr 222 km [hr 207 km/hr Asshown by these tests, what is important is that the insert be formed oftwo plies of cords which cross and are triangulated by the carcasscords. If one uses only a single ply, the improvement is insignificant.

FIG. 3 shows in radial section a tire of size 185 X 14 XAs in accordancewith the invention.

As compared with the tire shown in FIGS. 1 and 2, a number ofdifferences are noted, particularly the following. The carcass iscomposed of two plies -7 and 8 which, in the areas of the sidewallsclose to the crown 2 and of the steel wires 5 are separated by profiledpieces of hard rubber 9 of lenticular cross section. The crown ply 13 isdivided into two sections 13A and 13B separated from each other at themedian plane M-M' by a space of a few millimeters. This space is coveredby a ply 13C which extends over each of the edges of the sections 13Aand 13B adjacent this space. As in the case of FIG. 1, the inserts 15are composed of a ply of polyamide cables which is folded into twosections 15A and and 15B of a size of 40 and 28 mm, respectively, andprotruding from the ply 12 by a distance of about 8 mm, namely by thesame amount as that by which the ply l2 protrudes from the plies 13A and13B. The cables of the inserts 15 are identical to those of the inserts15 of FIGS. 1 and 2 and inclined about i 15 to the median plane M-M.

The use of inserts 15 of nylon cables instead of inserts made in theform of profiled rubber piecesretaining the same form for the carcassand the tread reinforcement has made it possible to increase the maximumspeed by 30 km/hr, which is a considerable gain for a minimum change inappearance.

Although the examples illustrated in the figures refer to tires forpassenger cars, the invention is not limited to this type of tire andmay be used on tires for utility vehicles such as trucks, deliverytrucks, busses, etc., and in general in all cases in which a tearing mayoccur between the carcass and the tread reinforcement. It is, of course,advisable to use inserts of cables that have suitable characteristicsfor the tire sizes in question.

Thus there is provided in accordance with the inven tion a novel andhighly effective tire capable of traveling safely under heavy loads andat high speeds. Many modifications of the preferred embodimentsdescribed herein will readily occur to those skilled in the art uponstudy of the present disclosure. Accordingly, the invention is to beconstrued as including all the embodiments thereof within the scope ofthe appended claims.

I claim:

1. A tire comprising a carcass of radial cords and a treadreinforcement, said tread reinforcement comprising at least two treadplies with staggered edges and being positioned in closel spaced apartrelation to the carcass 1n the central p0 ion thereof, furthercomprising interposed fittings of wedge-shaped cross section betweensaid carcass and said tread reinforcement filling the space between saidcarcass and said tread reinforcement at each edge of said treadreinforcement, each of said fittings comprising two interposed plies ofdifferent widths, said interposed plies comprising cords forming atriangulated structure with said radial cords and extending laterallybeyond the tread reinforcement over a distance of the same order ofmagnitude as the stagger spacing of the crown ply edges. I

2. A tire according to claim 1 wherein the cords of said interposedplies are inclined 10 to 30 to the longitudinal direction of the tire.

3. A tire according to claim 1 wherein the cords of said interposedplies are made of a material that contracts under heat.

4. A tire according to claim 1 wherein the cords of said interposedplies are made of polyamide.

5. A tire according to claim 1 wherein the cords of said interposedplies are of sufficiently small diameter and said interposed plies aresufficiently closely spaced apart that said interposed fittings do notnecessitate displacement of said carcass and said tread reinforcementwith respect to each other.

6. A tire according to claim 1 for use on a passenger car wherein thecords of said interposed plies are made

1. A tire comprising a carcass of radial cords and a treadreinforcement, said tread reinforcement comprising at least two treadplies with staggered edges and being positioned in closely spaced apartrelation to the carcass in the central portion thereof, furthercomprising interposed fittings of wedge-shaped cross section betweensaid carcass and said tread reinforcement filling the space between saidcarcass and said tread reinforcement at each edge of said treadreinforcement, each of said fittings comprising two interposed plies ofdifferent widths, said interposed plies comprising cords forming atriangulated structure with said radial cords and extending laterallybeyond the tread reinforcement over a distance of the same order ofmagnitude as the stagger spacing of the crown ply edges.
 1. A tirecomprising a carcass of radial cords and a tread reinforcement, saidtread reinforcement comprising at least two tread plies with staggerededges and being positioned in closely spaced apart relation to thecarcass in the central portion thereof, further comprising interposedfittings of wedge-shaped cross section between said carcass and saidtread reinforcement filling the space between said carcass and saidtread reinforcement at each edge of said tread reinforcement, each ofsaid fittings comprising two interposed plies of different widths, saidinterposed plies comprising cords forming a triangulated structure withsaid radial cords and extending laterally beyond the tread reinforcementover a distance of the same order of magnitude as the stagger spacing ofthe crown ply edges.
 2. A tire according to claim 1 wherein the cords ofsaid interposed plies are inclined 10* to 30* to the longitudinaldirection of the tire.
 3. A tire according to claim 1 wherein the cordsof said interposed plies are made of a material that contracts underheat.
 4. A tire according to claim 1 wherein the cords of saidinterposed plies are made of polyamide.
 5. A tire according to claim 1wherein the cords of said interposed plies are of sufficiently smalldiameter and said interposed plies are sufficiently closely spaced apartthat said interposed fittings do not necessitate displacement of saidcarcass and said tread reinforcement with respect to each other.
 6. Atire according to claim 1 for use on a passenger car wherein the cordsof said interposed plies are made of polyamide and have a diameter notexceeding 0.5 mm.